▎ 摘　　要

Plane wave based ab initio DTF all valence electron spin polarized calculations are reported for the electronic structure and geometry of differently shaped graphene molecules. These polycyclic hydrocarbon molecules comprise four series: D (2h) symmetric linear polyacenes C4m+2 H2m+4 (m = 2, ..., 25); D 6h hexagulenes with zigzag edges C-6m** 2 H-6m (m = 2, ..., 10); D-6h hexagulenes with crenelated edges C6(3m ** 2-3m+1) H6(2m-1) (m = 2, ..., 6); D-3h zigzag edged triangulenes Cm**2 +4m+1 H-6m (m = 2, ... 15). The systems variously display ground states that are spin paired singlet (S = 0), singlet anti-ferromagnetically ordered diradical and spin polarized S = 1/2 (m -1). Molecules with zigzag edges show evidence of electron delocalization along the perimeters with some bond alternation at the corners. In the acenes the spin paired singlet state of the short members switches to a singlet diradical at m approximate to 7-8 and this remains as the ground state for larger m. In contrast the triangulenes are magnetic and the atomic charge and spin density changes monotonically with distance from center to perimeter. In the hexagonal systems the development of a graphene core region, where the CC bonds are 142 pm, extends to within a few CC bonds of the perimeter atoms. Zigzag hexagulenes have a spin paired singlet ground state for m ]